Large deposits of laterite ores that contain high concentrations (&gt;5%) of cobalt and nickel exist world wide in the equatorial regions. Laterite consists of iron and manganese oxides and hydrates (mostly goethite and manganese wad) that contain nickel and cobalt as minor impurities.
There are several commercial processes for refining laterite ores. The predominant processes involve pyrometallugical refining which includes drying, reductive roasting, smelting and/or matte smelting. These processes are energy intensive, expensive, and cause air pollution.
To overcome these problems, a hydrometallurgical process is desirable. One such process, sulfuric acid pressure leach has been developed that is in practice at only one plant in the world (Kerfoot, Derek G. E. and Robert Weir [1988] "The Hydro And Electrometallurgy of Nickel And Cobalt", Sherritt Gordon Mones Limited, Fort Saskatchewan, Alberta, Canada T8L 2P2, Extractive Metallurgy of Nickel and Cobalt, edited by G. P. Troler and C. A. Landolt, The Metallurgical Society, pp. 241-267). Pressure acid leach processing, like smelting, has several drawbacks that have kept it from being widely used. Two of the drawbacks for using acid leach processing are that it utilizes very aggressive leach solutions and requires expensive autoclaves. Also, the pregnant leach solutions from pressurized acid leaching contain high concentrations of iron and manganese which consume acid and interfere with metal recovery.
The process described here is a hydrometallurgical process that uses less aggressive leaching solutions, is performed at atmospheric pressure, and produces a purer leach solution which represents a significant advancement in the art of cobalt and nickel refining.